Now, spoilers below!
I liked where it seems that they're going with the episodes with the "flashsideways", exploring an alternate reality where the plane doesn't crash but the characters are still, you know, mostly the same. I dug the scene with fake Locke/the smoke monster (mystery revealed!) and am definitely interested to see what he's going to be up to next. I liked the stories in 2004 with the main cast in the wreckage of the hatch (why did Juliet have to die...again!), but the stuff with the Temple kinda bored me. Partially because I can't take a guy who looks like this at all seriously.

So overall I enjoyed the episode but it wasn't one of my favorites. It looks like this season will be good, though.

Haven't been keeping up, or want a refresher? Here's a 8:15 recap of Seasons 1-5...blah, no direct link, but it's near the bottom of this article.

Maureen Ryan of the Chicago Tribune did a 10,000 word interview with Damon Lindelof and Carlton Cuse, the executive producers. Here's part 1 which is definitely worth reading (no spoilers for Season 6).